This document shoudl help - http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1004048
But please pay special attention to this note:
Note: One IP to one IP connections over multiple NICs is not supported. (Host A one connection session to Host B uses only one NIC).
This is due to the way the ESXi host handles load balancing -